feat(phase1): add image storage utilities

- Create backend/services/image_storage.py with 4 core functions:
  - sanitize_filename(): remove unsafe chars, limit to 255 chars, convert to lowercase
  - get_unique_filename(): handle collisions with UUID suffix (format: {name}_{uuid8}_{variant}.jpg)
  - ensure_image_directories(): create /images/ root and category subdirs on startup
  - save_image(): save bytes to /images/{category}/{filename}, returns relative path
- Create comprehensive test suite (22 tests) covering all functionality
- Integrate ensure_image_directories() into FastAPI startup event
- Directory structure: /images/{category}/{filename}
- Collision handling: auto-suffix with UUID if filename exists
- All tests passing, pathlib.Path for safe operations

venv/lib/python3.12/site-packages/jiter/__init__.py

@@ -0,0 +1,5 @@
+from .jiter import *
+
+__doc__ = jiter.__doc__
+if hasattr(jiter, "__all__"):
+    __all__ = jiter.__all__

venv/lib/python3.12/site-packages/jiter/__init__.pyi

@@ -0,0 +1,68 @@
+import decimal
+from typing import Any, Literal
+
+def from_json(
+    json_data: bytes,
+    /,
+    *,
+    allow_inf_nan: bool = True,
+    cache_mode: Literal[True, False, 'all', 'keys', 'none'] = 'all',
+    partial_mode: Literal[True, False, 'off', 'on', 'trailing-strings'] = False,
+    catch_duplicate_keys: bool = False,
+    float_mode: Literal['float', 'decimal', 'lossless-float'] = 'float',
+) -> Any:
+    """
+    Parse input bytes into a JSON object.
+
+    Arguments:
+        json_data: The JSON data to parse
+        allow_inf_nan: Whether to allow infinity (`Infinity` an `-Infinity`) and `NaN` values to float fields.
+            Defaults to True.
+        cache_mode: cache Python strings to improve performance at the cost of some memory usage
+            - True / 'all' - cache all strings
+            - 'keys' - cache only object keys
+            - False / 'none' - cache nothing
+        partial_mode: How to handle incomplete strings:
+            - False / 'off' - raise an exception if the input is incomplete
+            - True / 'on' - allow incomplete JSON but discard the last string if it is incomplete
+            - 'trailing-strings' - allow incomplete JSON, and include the last incomplete string in the output
+        catch_duplicate_keys: if True, raise an exception if objects contain the same key multiple times
+        float_mode: How to return floats: as a `float`, `Decimal` or `LosslessFloat`
+
+    Returns:
+        Python object built from the JSON input.
+    """
+
+def cache_clear() -> None:
+    """
+    Reset the string cache.
+    """
+
+def cache_usage() -> int:
+    """
+    get the size of the string cache.
+
+    Returns:
+        Size of the string cache in bytes.
+    """
+
+class LosslessFloat:
+    """
+    Represents a float from JSON, by holding the underlying bytes representing a float from JSON.
+    """
+    def __init__(self, json_float: bytes) -> None:
+        """Construct a LosslessFloat object from a JSON bytes slice"""
+
+    def as_decimal(self) -> decimal.Decimal:
+        """Construct a Python Decimal from the JSON bytes slice"""
+
+    def __float__(self) -> float:
+        """Construct a Python float from the JSON bytes slice"""
+
+    def __bytes__(self) -> bytes:
+        """Return the JSON bytes slice as bytes"""
+
+    def __str__(self) -> str:
+        """Return the JSON bytes slice as a string"""
+
+    def __repr__(self) -> str: ...